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<title>Hello, World</title>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Hello, World</h1>
<p>
This example brings up the words "Hello, World" moving up and down,
and in different colors.
<p> <hr>
<p> Header file:
<p> <pre>/****************************************************************************
** $Id: qt/hello.h 3.3.8 edited Jan 11 14:37 $
**
** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
**
** This file is part of an example program for Qt. This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/
#ifndef HELLO_H
#define HELLO_H
#include <<a href="qwidget-h.html">qwidget.h</a>>
class Hello : public <a href="qwidget.html">QWidget</a>
{
<a href="metaobjects.html#Q_OBJECT">Q_OBJECT</a>
public:
Hello( const char *text, QWidget *parent=0, const char *name=0 );
signals:
void clicked();
protected:
void mouseReleaseEvent( <a href="qmouseevent.html">QMouseEvent</a> * );
void paintEvent( <a href="qpaintevent.html">QPaintEvent</a> * );
private slots:
void animate();
private:
<a href="qstring.html">QString</a> t;
int b;
};
#endif
</pre>
<p> <hr>
<p> Implementation:
<p> <pre>/****************************************************************************
** $Id: qt/hello.cpp 3.3.8 edited Jan 11 14:37 $
**
** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
**
** This file is part of an example program for Qt. This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/
#include "hello.h"
#include <<a href="qpushbutton-h.html">qpushbutton.h</a>>
#include <<a href="qtimer-h.html">qtimer.h</a>>
#include <<a href="qpainter-h.html">qpainter.h</a>>
#include <<a href="qpixmap-h.html">qpixmap.h</a>>
/*
Constructs a Hello widget. Starts a 40 ms animation timer.
*/
<a name="f473"></a>Hello::Hello( const char *text, QWidget *parent, const char *name )
: <a href="qwidget.html">QWidget</a>(parent,name), t(text), b(0)
{
<a href="qtimer.html">QTimer</a> *timer = new <a href="qtimer.html">QTimer</a>(this);
<a name="x1640"></a> <a href="qobject.html#connect">connect</a>( timer, SIGNAL(<a href="qtimer.html#timeout">timeout</a>()), SLOT(animate()) );
<a name="x1639"></a> timer-><a href="qtimer.html#start">start</a>( 40 );
<a href="qwidget.html#resize">resize</a>( 260, 130 );
}
/*
This private slot is called each time the timer fires.
*/
void <a name="f474"></a>Hello::animate()
{
b = (b + 1) & 15;
<a href="qwidget.html#repaint">repaint</a>( FALSE );
}
/*
Handles mouse button release events for the Hello widget.
We emit the clicked() signal when the mouse is released inside
the widget.
*/
<a name="x1641"></a>void Hello::<a href="qwidget.html#mouseReleaseEvent">mouseReleaseEvent</a>( <a href="qmouseevent.html">QMouseEvent</a> *e )
{
if ( <a href="qwidget.html#rect">rect</a>().contains( e-><a href="qmouseevent.html#pos">pos</a>() ) )
emit clicked();
}
/*
Handles paint events for the Hello widget.
Flicker-free update. The text is first drawn in the pixmap and the
pixmap is then blt'ed to the screen.
*/
void Hello::<a href="qwidget.html#paintEvent">paintEvent</a>( <a href="qpaintevent.html">QPaintEvent</a> * )
{
static int sin_tbl[16] = {
0, 38, 71, 92, 100, 92, 71, 38, 0, -38, -71, -92, -100, -92, -71, -38};
if ( t.isEmpty() )
return;
// 1: Compute some sizes, positions etc.
<a href="qfontmetrics.html">QFontMetrics</a> fm = <a href="qwidget.html#fontMetrics">fontMetrics</a>();
<a name="x1631"></a> int w = fm.<a href="qfontmetrics.html#width">width</a>(t) + 20;
<a name="x1630"></a> int h = fm.<a href="qfontmetrics.html#height">height</a>() * 2;
int pmx = <a href="qwidget.html#width">width</a>()/2 - w/2;
int pmy = <a href="qwidget.html#height">height</a>()/2 - h/2;
// 2: Create the pixmap and fill it with the widget's background
<a href="qpixmap.html">QPixmap</a> pm( w, h );
<a name="x1638"></a> pm.<a href="qpixmap.html#fill">fill</a>( this, pmx, pmy );
// 3: Paint the pixmap. Cool wave effect
<a href="qpainter.html">QPainter</a> p;
int x = 10;
<a name="x1629"></a> int y = h/2 + fm.<a href="qfontmetrics.html#descent">descent</a>();
int i = 0;
<a name="x1633"></a> p.<a href="qpainter.html#begin">begin</a>( &pm );
<a name="x1636"></a> p.<a href="qpainter.html#setFont">setFont</a>( <a href="qwidget.html#font">font</a>() );
while ( !t[i].isNull() ) {
int i16 = (b+i) & 15;
p.<a href="qpainter.html#setPen">setPen</a>( QColor((15-i16)*16,255,255,QColor::Hsv) );
p.<a href="qpainter.html#drawText">drawText</a>( x, y-sin_tbl[i16]*h/800, t.mid(i,1), 1 );
x += fm.<a href="qfontmetrics.html#width">width</a>( t[i] );
i++;
}
<a name="x1635"></a> p.<a href="qpainter.html#end">end</a>();
// 4: Copy the pixmap to the Hello widget
<a href="qimage.html#bitBlt">bitBlt</a>( this, pmx, pmy, &pm );
}
</pre>
<p> <hr>
<p> Main:
<p> <pre>/****************************************************************************
** $Id: qt/main.cpp 3.3.8 edited Jan 11 14:37 $
**
** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
**
** This file is part of an example program for Qt. This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/
#include "hello.h"
#include <<a href="qapplication-h.html">qapplication.h</a>>
/*
The program starts here. It parses the command line and builds a message
string to be displayed by the Hello widget.
*/
int main( int argc, char **argv )
{
<a href="qapplication.html">QApplication</a> a(argc,argv);
<a href="qstring.html">QString</a> s;
for ( int i=1; i<argc; i++ ) {
s += argv[i];
if ( i<argc-1 )
s += " ";
}
if ( s.<a href="qstring.html#isEmpty">isEmpty</a>() )
s = "Hello, World";
Hello h( s );
#ifndef QT_NO_WIDGET_TOPEXTRA // for Qt/Embedded minimal build
h.<a href="qwidget.html#setCaption">setCaption</a>( "Qt says hello" );
#endif
QObject::<a href="qobject.html#connect">connect</a>( &h, SIGNAL(clicked()), &a, SLOT(<a href="qapplication.html#quit">quit</a>()) );
<a name="x1650"></a> h.<a href="qwidget.html#setFont">setFont</a>( QFont("times",32,QFont::Bold) ); // default font
<a name="x1648"></a> h.<a href="qwidget.html#setBackgroundColor">setBackgroundColor</a>( Qt::white ); // default bg color
a.<a href="qapplication.html#setMainWidget">setMainWidget</a>( &h );
h.<a href="qwidget.html#show">show</a>();
return a.<a href="qapplication.html#exec">exec</a>();
}
</pre>
<p>See also <a href="examples.html">Examples</a>.
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